Wireless communication system, base station apparatus, mobile station apparatus, wireless communication method and integrated circuit

ABSTRACT

A mobile station apparatus includes a transmission circuit or circuitry. The mobile station apparatus is configured to transmit a sounding reference signal (SRS) in a single carrier-Frequency Division Multiple Access (SC-FDMA) symbol corresponding to an SRS symbol. In addition, the mobile station apparatus is configured to, in a case that a region for SRS transmission on a given component carrier is extended based on a higher layer signal, transmit a first SRS in the SC-FDMA symbol, and transmit a second SRS in the extended region, where the first SRS is an SRS transmitted based on a first higher layer signal and the second SRS is an SRS transmitted based on a second higher layer signal and an SRS request in a physical downlink control channel (PDCCH).

RELATED APPLICATION

This application is a Continuation of copending application Ser. No.13/702,620 filed on Jan. 29, 2013, which is the U.S. National Phase ofPCT/JP2011/062380, filed May 30, 2011, and which claims priority toApplication No. 2010-132630 filed in Japan, on Jun. 10, 2010. The entirecontents of all of the above applications is hereby incorporated byreference.

TECHNICAL FIELD

The present invention relates to a wireless communication systemconfigured by a mobile station apparatus and a base station apparatus,and more particular, to a method for controlling transmission of areference signal for channel estimation of the mobile station apparatus.

BACKGROUND ART

A radio access system and the evolution of a radio network, of cellularmobile communication (hereinafter, also referred to as “long termevolution (LTE)” or “evolved universal terrestrial radio access(EUTRA)”), and a radio access system and a radio network that utilize afrequency band wider than that of LTE to realize faster datacommunication (hereinafter, also referred to as “long termevolution-advanced (LTE-A)” or “advanced evolved universal terrestrialradio access (A-EUTRA)”) have been conventionally studied in 3rdgeneration partnership project (3GPP).

As communication systems in LTE, an OFDMA (Orthogonal Frequency DivisionMultiple Access) system performing user multiplexing by usingsubcarriers orthogonal to each other, and an SC-FDMA (SingleCarrier-Frequency Division Multiple Access) system have been studied.That is, in a downlink, the OFDMA system that is a multi-carriercommunication system has been proposed, and in an uplink, the SC-FDMAsystem that is a single-carrier communication system has been proposed.

In contrast, as communication systems in LTE-A, in a downlink, it hasbeen studied to introduce the OFDMA system, and in an uplink, it hasbeen studied to introduce a clustered-SC-FDMA (also referred to asClustered-Single Carrier-Frequency Division Multiple Access, DFT-S-OFDMwith Spectrum Division Control, or DFT-precoded OFDM) system in additionto the SC-FDMA. Here, in LTE and LTE-A, the SC-FDMA system and theclustered-SC-FDMA system proposed as uplink communication systems havecharacteristics that can suppress PAPR (Peak to Average Power Ratio, ortransmission power) during data (information) transmission to be low dueto the characteristics of the single-carrier communication system (dueto single-carrier characteristics).

Furthermore, frequency bands used in ordinary wireless communicationsystems are contiguous in LTE-A, whereas it has been proposed that aplurality of contiguous and/or discontiguous frequency bands(hereinafter, also referred to as component carriers (CCs) or carriercomponents (CCs)) is compositely used, and thus, is operated as one widefrequency band (also referred to as a carrier aggregation). Furthermore,it has also been proposed that a frequency band used in downlinktransmission and a frequency band used in uplink transmission havedifferent frequency bandwidths (an asymmetric carrier aggregation) sothat a base station apparatus and a mobile station apparatus (UE: UserEquipment) use more flexibly a wide frequency band to performcommunications (Non-patent document 1).

FIG. 6 is a view illustrating a carrier-aggregated wirelesscommunication system in the conventional art. It is also referred to assymmetric carrier aggregation that a frequency band used in downlink(DL) communication and a frequency band used in uplink (UL)communication as shown in FIG. 6 have the same frequency bandwidth. Asshown in FIG. 6 a base station apparatus and a mobile station apparatuscan perform communication in a wide frequency band configured by aplurality of component carriers by compositely using the plurality ofcomponent carriers that is contiguous and/or discontiguous frequencybands.

FIG. 6 shows that as an example, a frequency band (or DL system band (DLsystem bandwidth)) used in downlink transmission that has a bandwidth of100 MHz is configured by five downlink component carriers (DCC1:Downlink Component Carrier 1, DCC2, DCC3, DCC4, and DCC5) each having abandwidth of 20 MHz. Furthermore, as an example, FIG. 6 shows that afrequency band (or UL system band (UL system bandwidth)) used in uplinktransmission that has a bandwidth of 100 MHz is configured by fiveuplink component carriers (UCC1: Uplink Component Carrier 1, UCC2, UCC3,UCC4, and UCC5) each having a bandwidth of 20 MHz.

In FIG. 6, downlink channels such as a physical downlink control channel(PDCCH) and a physical downlink shared channel (PDSCH) are assigned inrespective downlink component carriers.

The base station apparatus allocates (schedules) downlink controlinformation (DCI) for transmitting a downlink transport blocktransmitted by using a PDSCH to the mobile station apparatus by using aPDCCH. The base station apparatus transmits a downlink transport blockto the mobile station apparatus by using a PDSCH. Here, in FIG. 6, thebase station apparatus can transmit, to the mobile station apparatus, upto five downlink transport blocks (or PDSCHs) at maximum in the samesubframe.

Furthermore, uplink channels such as a physical uplink control channel(PUCCH) and a physical uplink shared channel (PUSCH) are assigned inrespective uplink component carriers.

The mobile station apparatus transmits, to the base station apparatus,uplink control information (UCI) such as channel state information (CSI)indicating a downlink channel state, information indicating an ACK/NACK(Positive Acknowledgement/Negative Acknowledgement) in HARQ for adownlink transport block, and a scheduling request (SR) by using a PUCCHand/or a PUSCH. Here, in FIG. 6, the mobile station apparatus cantransmit, to the base station apparatus, up to five uplink transportblocks (or PUSCHs) at maximum in the same subframe.

Similarly, FIG. 7 is a view illustrating an asymmetricallycarrier-aggregated wireless communication system in the conventionalart. As shown in FIG. 7, the base station apparatus and the mobilestation apparatus can perform communication in a wide frequency band: bycausing a frequency band used in downlink transmission and a frequencyband used in uplink transmission to have different frequency bandwidths;and by compositely using component carriers that are contiguous and/ordiscontiguous frequency bands constituting these frequency bands.

FIG. 7 shows that as an example, a frequency band having a bandwidth of100 MHz and used in downlink transmission is configured by five downlinkcomponent carriers (DCC1, DCC2, DCC3, DCC4, and DCC5) each having abandwidth of 20 MHz. Furthermore, as an example, FIG. 7 shows that afrequency band having a bandwidth of 40 MHz and used in uplinktransmission is configured by two uplink component carriers (UCC1 andUCC2) each having a bandwidth of 20 MHz.

In FIG. 7, downlink/uplink channels are assigned in respectivedownlink/uplink component carriers. The base station apparatus allocates(schedules) a PDSCH to the mobile station apparatus by using a PDCCH,and transmits a downlink transport block to the mobile station apparatusby using the PDSCH. Here, in FIG. 7, the base station apparatus cantransmit, to the mobile station apparatus, up to five downlink transportblocks (or PDSCHs) at maximum in the same subframe.

Furthermore, the mobile station apparatus transmits, to the base stationapparatus, uplink control information such as channel state information,information indicating an ACK/NACK in HARQ for a downlink transportblock, and a scheduling request by using a PUCCH and/or a PUSCH. Here,in FIG. 7, the mobile station apparatus can transmit, to the basestation apparatus, up to two uplink transport blocks (or PUSCHs) atmaximum in the same subframe.

In LTE-A, a sounding reference signal (A-SRS: Aperiodic SoundingReference Signal) transmitted only when a transmission request isnotified by a PDCCH from the base station apparatus has been proposed.By including A-SRS transmission indication information (A-SRSactivation/deactivation) in a downlink control information (DCI) format(also referred to as a DCI format), the mobile station apparatus candetermine whether or not the base station apparatus requeststransmission of an A-SRS, and can dynamically perform transmissioncontrol of an A-SRS. Furthermore, it has been proposed that the basestation apparatus: indicates the mobile station apparatus to performtransmission of an A-SRS, by using a downlink control information format(also referred to as a DCI format, a downlink grant, or a downlinkassignment) for a downlink; and indicates the mobile station apparatusto perform transmission of an A-SRS, by using a downlink controlinformation format (also referred to as a DCI format, an UL grant, or anuplink assignment) for an uplink. Furthermore, it has been proposed toindicate an indication of transmission of an A-SRS by one bit (ormultiple bits) of an uplink grant or a downlink assignment, or apredetermined code point (Non-patent document 2).

RELATED ART DOCUMENTS Non-Patent Documents

Non-patent document 1: “Carrier aggregation in LTE-Advanced”, R1-082468,3GPP TSGRAN WG1 Meeting #53bis, Jun. 30-Jul. 4, 2008.

Non-patent document 2: “LTE-A Dynamic Aperiodic SRS—Duration, Timing,and Carrier Aggregation”, R1-103187, 3GPP TSG-RAN1 Meeting #61, May10-14, 2010.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, in the conventional art, a mobile station apparatus indicatedto perform transmission of an A-SRS by a base station apparatustransmits an A-SRS to the base station apparatus without switchingparameters used in A-SRS transmission. That is, the mobile stationapparatus transmits an A-SRS to the base station apparatus by assigningthe A-SRS in a PUSCH resource (a part of the PUSCH resource) scheduledby the base station apparatus (inband A-SRS transmission). For example,the mobile station apparatus transmits an A-SRS to the base stationapparatus in the transmission bandwidth of the same bandwidth as a PUSCHresource scheduled by the base station apparatus.

Furthermore, the mobile station apparatus transmits the A-SRS to thebase station apparatus by assigning an A-SRS in a resource set insetting information different from setting information for a PUSCHresource by the base station apparatus (outbandA-SRS transmission). Forexample, the mobile station apparatus transmits an A-SRS to the basestation apparatus in a wide transmission bandwidth set by the basestation apparatus.

Here, when the mobile station apparatus performs communication with thebase station apparatus in an environment of good communication quality,even if an A-SRS is transmitted inband, the base station apparatus canperform channel estimation only within the range of a PUSCH resourcescheduled for the mobile station apparatus, cannot provide theimprovement of communication quality due to frequency selectionscheduling, and thus, cannot perform effective communication.Furthermore, when the mobile station apparatus performs communicationwith the base station apparatus in an environment of poor communicationquality, even if an A-SRS is transmitted outband, the accuracy ofchannel estimation by the base station apparatus is degraded, and it isimpossible to perform effective communication. That is, in theconventional art, since the mobile station apparatus indicated toperform transmission of an A-SRS by the base station apparatus transmitsan A-SRS to the base station apparatus without switching parameters usedin A-SRS transmission, there has been a problem that it is impossible toperform effective communication between the base station apparatus andthe mobile station apparatus.

The present invention has been made in view of the above-describedpoints, and has an objective to provide a wireless communication system,a base station apparatus, a mobile station apparatus, a wirelesscommunication method, and an integrated circuit that can performeffective communication between the base station apparatus and themobile station apparatus based on an A-SRS transmitted from the mobilestation apparatus.

Means of Solving the Problems

(1) In order to achieve the above-described objective, the presentinvention takes measures as described below. That is, according to thepresent invention, there is provided a wireless communication system inwhich a base station apparatus and a mobile station apparatus performwireless communication, wherein the base station apparatus: notifies themobile station apparatus of a radio resource control signal includingtransmission control information for setting, to the mobile stationapparatus, whether to transmit a first sounding reference signalassigned in a physical uplink shared channel resource, or to transmit asecond sounding reference signal assigned in a resource different fromthe physical uplink shared channel resource; and notifies the mobilestation apparatus of an uplink grant including an indication oftransmission of the sounding reference signal, and wherein the mobilestation apparatus, when the indication of transmission of the soundingreference signal included in the uplink grant is received: transmits thefirst sounding reference signal to the base station apparatus, when thetransmission of the first sounding reference signal is set by thetransmission control information; and transmits the second soundingreference signal to the base station apparatus, when the transmission ofthe second sounding reference signal is set by the transmission controlinformation.

(2) According to the present invention, there is provided a wirelesscommunication system in which a base station apparatus and a mobilestation apparatus perform wireless communication, wherein the basestation apparatus notifies the mobile station apparatus of an uplinkgrant including control information indicating whether to transmit afirst sounding reference signal assigned in a physical uplink sharedchannel resource, or to transmit a second sounding reference signalassigned in a resource different from the physical uplink shared channelresource, and wherein the mobile station apparatus transmits the firstsounding reference signal or the second sounding reference signal to thebase station apparatus, based on the control information included in theuplink grant.

(3) According to the present invention, there is provided a wirelesscommunication system in which a base station apparatus and a mobilestation apparatus perform wireless communication, wherein the basestation apparatus: sets transmission indication information included inan uplink grant as a first value, when indicating the mobile stationapparatus to perform transmission of a first sounding reference signalassigned in a physical uplink shared channel resource; sets thetransmission indication information as a second value, when indicatingthe mobile station apparatus to perform transmission of a secondsounding reference signal assigned in a resource different from thephysical uplink shared channel resource; and notifies the mobile stationapparatus of the uplink grant including the transmission indicationinformation set at the first value or the second value, and wherein themobile station apparatus: transmits the first sounding reference signalto the base station apparatus, when the transmission indicationinformation included in the uplink grant is the first value; andtransmits the second sounding reference signal to the base stationapparatus, when the transmission indication information included in theuplink grant is the second value.

(4) According to the present invention, there is provided a wirelesscommunication system in which a base station apparatus and a mobilestation apparatus perform wireless communication, wherein the basestation apparatus: sets transmission indication information of one bitincluded in an uplink grant at a predetermined value, when indicatingthe mobile station apparatus to perform transmission of a first soundingreference signal assigned in a physical uplink shared channel resource;sets first control information included in the uplink grant at apredetermined code point, when indicating the mobile station apparatusto perform transmission of a second sounding reference signal assignedin a resource different from the physical uplink shared channelresource; sets the indication of transmission of the sounding referencesignal with the transmission indication information or the first controlinformation; notifies the mobile station apparatus of the uplink grantincluding the transmission indication information set at thepredetermined value or the first control information set at thepredetermined code point; and notifies the mobile station apparatus ofthe uplink grant including the indication of transmission of thesounding reference signal, and wherein the mobile station apparatus:transmits the first sounding reference signal to the base stationapparatus, when the transmission indication information included in theuplink grant indicates the indication of transmission of the soundingreference signal; and transmits the second sounding reference signal tothe base station apparatus, when the first control information includedin the uplink grant is the predetermined code point.

(5) According to the present invention, there is provided the wirelesscommunication system according to (1), wherein the base stationapparatus sets the indication of transmission of the sounding referencesignal with transmission indication information of one bit or firstcontrol information that is a predetermined code point.

(6) According to the present invention, there is provided the wirelesscommunication system according to (1), wherein the base stationapparatus sets the transmission control information for each uplinkcomponent carrier.

(7) According to the present invention, there is provided the wirelesscommunication system according to (4), wherein the base stationapparatus notifies the mobile station apparatus of the uplink grantincluding a parameter of the second sounding reference signal and thefirst control information, and wherein the mobile station apparatustransmits, in accordance with the uplink grant, to the base stationapparatus, the second sounding reference signal in which the parameterincluded in the uplink grant is set, when the first control informationis the predetermined code point.

(8) According to the present invention, there is provided a base stationapparatus that performs wireless communication with a mobile stationapparatus. The base station apparatus at least includes: a unit thatnotifies the mobile station apparatus of a radio resource control signalincluding transmission control information for setting, to the mobilestation apparatus, whether to transmit a first sounding reference signalassigned in a physical uplink shared channel resource, or to transmit asecond sounding reference signal assigned in a resource different fromthe physical uplink shared channel resource; and a unit that notifiesthe mobile station apparatus of an uplink grant including an indicationof transmission of a sounding reference signal.

(9) According to the present invention, there is provided a base stationapparatus that performs wireless communication with a mobile stationapparatus. The base station apparatus at least includes a unit thatnotifies the mobile station apparatus of an uplink grant includingcontrol information indicating whether to transmit a first soundingreference signal assigned in a physical uplink shared channel resource,or to transmit a second sounding reference signal assigned in a resourcedifferent from the physical uplink shared channel resource.

(10) According to the present invention, there is provided a basestation apparatus that performs wireless communication with a mobilestation apparatus. The base station apparatus at least includes: a unitthat sets transmission indication information included in an uplinkgrant as a first value, when indicating the mobile station apparatus toperform transmission of a first sounding reference signal assigned in aphysical uplink shared channel resource; a unit that sets thetransmission indication information as a second value, when indicatingthe mobile station apparatus to perform transmission of a secondsounding reference signal assigned in a resource different from thephysical uplink shared channel resource; and a unit that notifies themobile station apparatus of the uplink grant including the transmissionindication information set at the first value or the second value.

(11) According to the present invention, there is provided a basestation apparatus that performs wireless communication with a mobilestation apparatus. The base station apparatus at least includes: a unitthat sets transmission indication information of one bit included in anuplink grant at a predetermined value, when indicating the mobilestation apparatus to perform transmission of a first sounding referencesignal assigned in a physical uplink shared channel resource; a unitthat sets first control information included in the uplink grant at apredetermined code point, when indicating the mobile station apparatusto perform transmission of a second sounding reference signal assignedin a resource different from the physical uplink shared channelresource; a unit that sets the indication of transmission of thesounding reference signal with the transmission indication informationor the first control information; a unit that notifies the mobilestation apparatus of the uplink grant including the transmissionindication information set at the predetermined value or the firstcontrol information set at the predetermined code point; and a unit thatnotifies the mobile station apparatus of the uplink grant including theindication of transmission of the sounding reference signal.

(12) According to the present invention, there is provided a mobilestation apparatus that performs wireless communication with a basestation apparatus. The mobile station apparatus at least includes: aunit that receives transmission control information notified from thebase station apparatus; a unit that receives an uplink grant notifiedfrom the base station apparatus; and when receiving an indication oftransmission of a sounding reference signal included in the uplinkgrant: a unit that transmits a first sounding reference signal to thebase station apparatus, when the transmission of the first soundingreference signal is set by the transmission control information; and aunit that transmits a second sounding reference signal to the basestation apparatus, when the transmission of the second soundingreference signal is set by the transmission control information.

(13) According to the present invention, there is provided a mobilestation apparatus that performs wireless communication with a basestation apparatus. The mobile station apparatus at least includes: aunit that receives an uplink grant notified from the base stationapparatus; and a unit that transmits a first sounding reference signalor a second sounding reference signal to the base station apparatus,based on control information included in the uplink grant.

(14) According to the present invention, there is provided a mobilestation apparatus that performs wireless communication with a basestation apparatus. The mobile station apparatus at least includes: aunit that receives an uplink grant notified from the base stationapparatus; a unit that transmits a first sounding reference signal tothe base station apparatus, when transmission indication informationincluded in the uplink grant is a first value; and a unit that transmitsa second sounding reference signal to the base station apparatus, whenthe transmission indication information included in the uplink grant isa second value.

(15) According to the present invention, there is provided a mobilestation apparatus that performs wireless communication with a basestation apparatus. The mobile station apparatus at least includes: aunit that receives an uplink grant notified from the base stationapparatus; a unit that transmits a first sounding reference signal tothe base station apparatus, when transmission indication informationincluded in the uplink grant indicates an indication of transmission ofa sounding reference signal; and a unit that transmits a second soundingreference signal to the base station apparatus, when first controlinformation included in the uplink grant is a predetermined code point.

(16) According to the present invention, there is provided a wirelesscommunication method in which a base station apparatus and a mobilestation apparatus perform wireless communication, the method comprisingat least the steps of: in the base station apparatus, notifying themobile station apparatus of transmission control information forsetting, to the mobile station apparatus, whether to transmit a firstsounding reference signal assigned in a physical uplink shared channelresource, or to transmit a second sounding reference signal assigned ina resource different from the physical uplink shared channel resource;and notifying the mobile station apparatus of an uplink grant includingan indication of transmission of the sounding reference signal, and inthe mobile station apparatus, when the indication of transmission of thesounding reference signal included in the uplink grant is received:transmitting the first sounding reference signal to the base stationapparatus, when the transmission of the first sounding reference signalis set by the transmission control information; and transmitting thesecond sounding reference signal to the base station apparatus, when thetransmission of the second sounding reference signal is set by thetransmission control information.

(17) According to the present invention, there is provided a wirelesscommunication method by which a base station apparatus and a mobilestation apparatus perform wireless communication, the method comprisingat least the steps of: in the base station apparatus, notifying themobile station apparatus of an uplink grant including controlinformation indicating whether to transmit a first sounding referencesignal assigned in a physical uplink shared channel resource, or totransmit a second sounding reference signal assigned in a resourcedifferent from the physical uplink shared channel resource, and in themobile station apparatus, transmitting the first sounding referencesignal or the second sounding reference signal to the base stationapparatus, based on the control information included in the uplinkgrant.

(18) According to the present invention, there is provided a wirelesscommunication method by which a base station apparatus and a mobilestation apparatus perform wireless communication, the method comprisingat least the steps of: in the base station apparatus, settingtransmission indication information included in an uplink grant as afirst value, when the base station apparatus indicates the mobilestation apparatus to perform transmission of a first sounding referencesignal assigned in a physical uplink shared channel resource; settingthe transmission indication information as a second value, when the basestation apparatus indicates the mobile station apparatus to performtransmission of a second sounding reference signal assigned in aresource different from the physical uplink shared channel resource; andnotifying the mobile station apparatus of the uplink grant including thetransmission indication information set at the first value or the secondvalue, and in the mobile station apparatus, transmitting the firstsounding reference signal to the base station apparatus, when thetransmission indication information included in the uplink grant is thefirst value; and transmitting the second sounding reference signal tothe base station apparatus, when the transmission indication informationincluded in the uplink grant is the second value.

(19) According to the present invention, there is provided a wirelesscommunication method by which a base station apparatus and a mobilestation apparatus perform wireless communication, the method comprisingat least the steps of: in the base station apparatus, settingtransmission indication information of one bit included in an uplinkgrant at a predetermined value, when the base station apparatusindicates the mobile station apparatus to perform transmission of afirst sounding reference signal assigned in a physical uplink sharedchannel resource; setting first control information included in theuplink grant at a predetermined code point, when the base stationapparatus indicates the mobile station apparatus to perform transmissionof a second sounding reference signal assigned in a resource differentfrom the physical uplink shared channel resource; setting the indicationof transmission of the sounding reference signal with the transmissionindication information or the first control information; notifying themobile station apparatus of the uplink grant including the transmissionindication information set at the predetermined value or the firstcontrol information set at the predetermined code point; and notifyingthe mobile station apparatus of the uplink grant including theindication of transmission of the sounding reference signal, and in themobile station apparatus, transmitting the first sounding referencesignal to the base station apparatus, when the transmission indicationinformation included in the uplink grant indicates the indication oftransmission of the sounding reference signal; and transmitting thesecond sounding reference signal to the base station apparatus, when thefirst control information included in the uplink grant is thepredetermined code point.

(20) According to the present invention, there is provided an integratedcircuit which, when mounted in a base station apparatus, causes the basestation apparatus to perform a plurality of functions, the integratedcircuit causing the base station apparatus to perform functions of:notifying a mobile station apparatus of transmission control informationfor setting, to the mobile station apparatus, whether to transmit afirst sounding reference signal assigned in a physical uplink sharedchannel resource, or to transmit a second sounding reference signalassigned in a resource different from the physical uplink shared channelresource; and notifying the mobile station apparatus of an uplink grantincluding an indication of transmission of a sounding reference signal.

(21) According to the present invention, there is provided an integratedcircuit which, when mounted in a base station apparatus, causes the basestation apparatus to perform a plurality of functions, the integratedcircuit causing the base station apparatus to perform a function ofnotifying a mobile station apparatus of an uplink grant includingcontrol information indicating whether to transmit a first soundingreference signal assigned in a physical uplink shared channel resource,or to transmit a second sounding reference signal assigned in a resourcedifferent from the physical uplink shared channel resource.

(22) According to the present invention, there is provided an integratedcircuit which, when mounted in a base station apparatus, causes the basestation apparatus to perform a plurality of functions, the integratedcircuit causing the base station apparatus to perform functions of:setting transmission indication information included in an uplink grantas a first value, when indicating a mobile station apparatus to performtransmission of a first sounding reference signal assigned in a physicaluplink shared channel resource; setting the transmission indicationinformation as a second value, when indicating the mobile stationapparatus to perform transmission of a second sounding reference signalassigned in a resource different from the physical uplink shared channelresource; and notifying the mobile station apparatus of the uplink grantincluding the transmission indication information set at the first valueor the second value.

(23) According to the present invention, there is provided an integratedcircuit which, when mounted in a base station apparatus, causes the basestation apparatus to perform a plurality of functions, the integratedcircuit causing the base station apparatus to perform functions of:setting transmission indication information of one bit included in anuplink grant at a predetermined value, when indicating a mobile stationapparatus to perform transmission of a first sounding reference signalassigned in a physical uplink shared channel resource; setting firstcontrol information included in the uplink grant at a predetermined codepoint, when indicating the mobile station apparatus to performtransmission of a second sounding reference signal assigned in aresource different from the physical uplink shared channel resource;setting the indication of transmission of the sounding reference signalwith the transmission indication information or the first controlinformation; notifying the mobile station apparatus of the uplink grantincluding the transmission indication information set at thepredetermined value or the first control information set at thepredetermined code point; and notifying the mobile station apparatus ofthe uplink grant including the indication of transmission of thesounding reference signal.

(24) According to the present invention, there is provided an integratedcircuit which, when mounted in a base station apparatus, causes a mobilestation apparatus to perform a plurality of functions, the integratedcircuit causing the mobile station apparatus to perform functions of:receiving transmission control information notified from abase stationapparatus; receiving an uplink grant notified from the base stationapparatus; and when an indication of transmission of a soundingreference signal included in the uplink grant is received: transmittinga first sounding reference signal to the base station apparatus, whenthe transmission of the first sounding reference signal is set by thetransmission control information; and transmitting a second soundingreference signal to the base station apparatus, when the transmission ofthe second sounding reference signal is set by the transmission controlinformation.

(25) According to the present invention, there is provided an integratedcircuit which, when mounted in a base station apparatus, causes a mobilestation apparatus to perform a plurality of functions, the integratedcircuit causing the mobile station apparatus to perform functions of:receiving an uplink grant notified from a base station apparatus; andtransmitting a first sounding reference signal or a second soundingreference signal to the base station apparatus, based on controlinformation included in the uplink grant.

(26) According to the present invention, there is provided an integratedcircuit which, when mounted in a base station apparatus, causes a mobilestation apparatus to perform a plurality of functions, the integratedcircuit causing the mobile station apparatus to perform functions of:receiving an uplink grant notified from a base station apparatus; andtransmitting a first sounding reference signal to the base stationapparatus, when transmission indication information included in theuplink grant is a first value; and transmitting a second soundingreference signal to the base station apparatus, when the transmissionindication information included in the uplink grant is a second value.

(27) According to the present invention, there is provided an integratedcircuit which, when mounted in a base station apparatus, causes a mobilestation apparatus to perform a plurality of functions, the integratedcircuit causing the mobile station apparatus to perform functions of:receiving an uplink grant notified from a base station apparatus;transmitting a first sounding reference signal to the base stationapparatus, when transmission indication information included in theuplink grant indicates an indication of transmission of a soundingreference signal; and transmitting a second sounding reference signal tothe base station apparatus, when first control information included inthe uplink grant is a predetermined code point.

(28) According to the present invention, there is provided a basestation apparatus that performs wireless communication with a mobilestation apparatus. The base station apparatus at least includes a basestation side transmission unit that notifies the mobile stationapparatus of: a radio resource control signal including transmissioncontrol information for setting, to the mobile station apparatus,whether to transmit a first sounding reference signal assigned in aphysical uplink shared channel resource, or to transmit a secondsounding reference signal assigned in a resource different from thephysical uplink shared channel resource is transmitted; and an uplinkgrant including an indication of transmission of a sounding referencesignal.

(29) According to the present invention, there is provided a basestation apparatus that performs wireless communication with a mobilestation apparatus. The base station apparatus at least includes a basestation side transmission unit that notifies the mobile stationapparatus of an uplink grant including control information indicatingwhether to transmit a first sounding reference signal assigned in aphysical uplink shared channel resource, or to transmit a secondsounding reference signal assigned in a resource different from thephysical uplink shared channel resource.

(30) According to the present invention, there is provided a basestation apparatus that performs wireless communication with a mobilestation apparatus. The base station apparatus at least includes: a basestation side scheduling unit that: sets transmission indicationinformation included in an uplink grant as a first value, whenindicating the mobile station apparatus to perform transmission of afirst sounding reference signal assigned in a physical uplink sharedchannel resource; and sets the transmission indication information as asecond value, when indicating the mobile station apparatus to performtransmission of a second sounding reference signal assigned in aresource different from the physical uplink shared channel resource; anda base station side transmission unit that notifies the mobile stationapparatus of the uplink grant including the transmission indicationinformation set at the first value or the second value.

(31) According to the present invention, there is provided a basestation apparatus that performs wireless communication with a mobilestation apparatus. The base station apparatus at least includes: a basestation side scheduling unit that: sets transmission indicationinformation of one bit included in an uplink grant at a predeterminedvalue, when indicating the mobile station apparatus to performtransmission of a first sounding reference signal assigned in a physicaluplink shared channel resource; sets first control information includedin the uplink grant at a predetermined code point, when indicating themobile station apparatus to perform transmission of a second soundingreference signal assigned in a resource different from the physicaluplink shared channel resource; and sets the indication of transmissionof the sounding reference signal with the transmission indicationinformation or the first control information; and a base station sidetransmission unit that notifies the mobile station apparatus of: theuplink grant including the transmission indication information set atthe predetermined value or the first control information set at thepredetermined code point; and the uplink grant including the indicationof transmission of the sounding reference signal.

(32) According to the present invention, there is provided a mobilestation apparatus that performs wireless communication with a basestation apparatus. The mobile station apparatus at least includes: amobile station side reception unit that receives transmission controlinformation and an uplink grant notified from the base stationapparatus; and a mobile station side transmission unit that, whenreceiving an indication of transmission of a sounding reference signalincluded in the uplink grant: transmits a first sounding referencesignal to the base station apparatus, when transmission of the firstsounding reference signal is set by the transmission controlinformation; and transmits a second sounding reference signal to thebase station apparatus, when transmission of the second soundingreference signal is set by the transmission control information.

(33) According to the present invention, there is provided a mobilestation apparatus that performs wireless communication with a basestation apparatus, The mobile station apparatus at least includes: amobile station side reception unit that receives an uplink grantnotified from the base station apparatus; and a mobile station sidetransmission unit that transmits a first sounding reference signal or asecond sounding reference signal to the base station apparatus, based oncontrol information included in the uplink grant.

(34) According to the present invention, there is provided a mobilestation apparatus that performs wireless communication with a basestation apparatus. The mobile station apparatus at least includes: amobile station side reception unit that receives an uplink grantnotified from the base station apparatus; and a mobile station sidetransmission unit that: transmits a first sounding reference signal tothe base station apparatus, when transmission indication informationincluded in the uplink grant is a first value; and transmits a secondsounding reference signal to the base station apparatus, when thetransmission indication information included in the uplink grant is asecond value.

(35) According to the present invention, there is provided a mobilestation apparatus that performs wireless communication with a basestation apparatus. The mobile station apparatus at least includes: amobile station side reception unit that receives an uplink grantnotified from the base station apparatus; and a mobile station sidetransmission unit that: transmits a first sounding reference signal tothe base station apparatus, when transmission indication informationincluded in the uplink grant indicates an indication of transmission ofa sounding reference signal; and transmits a second sounding referencesignal to the base station apparatus, when first control informationincluded in the uplink grant is a predetermined code point.

Advantages of the Invention

According to the present invention, it is possible to provide a mobilestation apparatus, abase station apparatus, a wireless communicationsystem, a wireless communication method, and an integrated circuit thatcan perform effective communication between the base station apparatusand the mobile station apparatus based on an A-SRS transmitted from themobile station apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a schematic functional structure of abase station apparatus 1 of the present invention.

FIG. 2 is a block diagram showing a schematic functional structure of amobile station apparatus 3 of the present invention.

FIGS. 3(a) and 3(b) are views showing an example of a DCI Formatincluding an indication of transmission of an A-SRS in a firstembodiment.

FIGS. 4(a) and 4(b) are views showing an example of a DCI Formatincluding an indication of transmission of an A-SRS in a secondembodiment.

FIGS. 5(a) and 5(b) are views showing an example of a DCI Formatincluding an indication of transmission of an A-SRS in a thirdembodiment.

FIG. 6 is a view showing an example of carrier aggregation in theconventional art.

FIG. 7 is a view showing an example of asymmetric carrier aggregation inthe conventional art.

FIGS. 8(a) and 8(b) are views showing schematic structures of an inbandA-SRS (a first A-SRS) and an outband A-SRS (a second A-SRS).

FIG. 9 is a view showing schematic structures of SRS resource allocationand frequency hopping (FH).

BEST MODES FOR CARRYING OUT THE INVENTION

Before the specific description of embodiments of the present inventionis given, outlines of communication techniques used in the presentinvention will be briefly described.

(Physical Channel)

The physical channels used in the present invention include a physicalbroadcast channel (PBCH), a physical downlink shared channel (PDSCH), aphysical downlink control channel (PDCCH), a downlink reference signal(DL-RS or Cell-specific Reference Signal), a physical uplink sharedchannel (PUSCH), a physical uplink control channel (PUCCH), a physicalrandom access channel (PRACH), an uplink reference signal (UL-RS), andthe like. Even if different kinds of physical channels are added, theyare applicable to the embodiments of the present invention describedbelow.

The physical broadcast channel is transmitted for the purpose ofnotifying a control parameter (broadcast information) commonly used formobile station apparatuses in a cell. Broadcast information which is notnotified by a PBCH and a resource for which is notified by a PDCCH, istransmitted by using a physical uplink shared channel. A cell global ID(Identity) or the like indicating a cell individual ID, is notified asbroadcast information. A broadcast channel (BCH) is mapped to a PBCH at40 ms intervals. The 40 ms timing is blindly detected (blind detection)in the mobile station apparatus. That is, for PBCH timing presentation,explicit signaling is not transmitted to the mobile station apparatus.Furthermore, a subframe including a PBCH can be decoded only by thesubframe (is self-decodable).

The physical downlink control channel is a downlink channel transmittedfrom a base station apparatus to the mobile station apparatus, and is achannel used to notify the mobile station apparatus of downlink controlinformation (DCI) such as: a downlink assignment including PDSCHresource allocation, and hybrid automatic repeat request (HARQ)information for downlink data (DL-SCH: Downlink-Shared Channel); anduplink transmission permission (an uplink grant) that is the resourceallocation of a physical uplink shared channel (PUSCH), and HARQinformation for uplink data (UL-SCH: Uplink Shared Channel).Furthermore, the PDCCH includes a plurality of control channel elements(CCEs), and the mobile station apparatus receives a PDCCH from the basestation apparatus by detecting the PDCCH including CCEs. This CCEincludes a plurality of resource element groups (also referred to asREGs or mini-CCEs) dispersed in the time domain and the frequencydomain. Here, the resource element is a unit resource composed of oneOFDM symbol (time domain) and one subcarrier (frequency domain).

A plurality of formats is prepared for downlink control informationtransmitted by a physical downlink control channel. The format ofdownlink control information (DCI) is referred to as a DCI Format. Forexample, DCI format used when the mobile station apparatus 3 transmits aPUSCH by one transmission antenna port, DCI format 0A used when themobile station apparatus 3 transmits a PUSCH by spatial multiplexing(SM) utilizing MIMO (Multiple Input Multiple Output), and the like areprepared as the DCI formats of an uplink grant.

Furthermore, DCI format 1 used when the base station apparatus transmitsa PDSCH by using one transmission antenna port or by using atransmission diversity scheme by a plurality of transmission antennaports, DCI format 1A having the smaller number of bits than DCI format1, DCI format 1C used for the radio resource allocation of paginginformation, or the like and having the further smaller number of bitsthan DCI format 1A, DCI format 2 used when the mobile station apparatustransmits a PDSCH by SM utilizing MIMO, and the like are prepared as theDCI formats of downlink assignments. In DCI format 0 and DCI format 1A,the sizes of these two DCI formats are made the same by inserting bitsinto the DCI format having the smaller number of bits, and a flag (Flagfor format 0/format 1A differentiation) for identifying the format isincluded therein.

Specifically, DCI format 0 that is an uplink grant includes controlinformation (also referred to as a field, a control information field,an information field, and a bit field) such as PDCCH formatidentification (Flag for format 0/format 1A differentiation)information, a frequency hopping flag, resource block assignment andhopping resource allocation information, modulation and coding schemeand redundancy version information, NDI (New Data Indicator)information, information of a transmission power control (TPC) commandfor a scheduled PUSCH, information of a cyclic shift for a DM-RS, CQItransmission indication (CQI request) information, padding bit (0padding) information, and cyclic redundancy check (CRC) information.

The PDCCH format identification information is information indicatingthe kind of DCI format of this downlink control information, i.e.,whether the DCI format is DCI format 0 or DCI format 1A. The resourceblock assignment and hopping resource allocation information isinformation indicating a PUSCH resource block assignment and resourceallocation in the case where hopping is performed. The modulation andcoding scheme and redundancy version information is informationindicating a modulation scheme, coding rate, and redundancy version of aPUSCH. The NDI information is information indicating whether the PUSCHis initially transmitted or retransmitted. The information of atransmission power control command for a PUSCH is information used forthe transmission power control of the PUSCH. The information of a cyclicshift for a DM-RS is information indicating a cyclic shift for a DM-RS.The padding bit (0 padding) information is a bit inserted so that thesizes of DCI format 0 and DCI format 1A are made the same, and the valueof the bit is set at “0”. When the base station apparatus requests aCQI, the CQI transmission indication information can indicate the mobilestation apparatus: to assign the CQI by utilizing a PUSCH resource; andto dynamically transmit it to the base station apparatus. The CQI atthis time is also referred to as an aperiodic CQI (A-CQI).

Specifically, DCI format 1A that is a downlink assignment includescontrol information (also referred to as a field, a control informationfield, an information field, and a bit field) such as PDCCH formatidentification (Flag for format 0/format 1A differentiation)information, information of localized/distributed VRB assignment flag ofvirtual resource blocks (VRBs), resource block assignment information,modulation and coding scheme (MCS) information, HARQ process numberinformation, NDI (New Data Indicator) information, redundancy version(RV) information, information of a transmission power control (TPC)command for a PUCCH, padding bit (0 padding) information, and cyclicredundancy check (CRC) information.

The PDCCH format identification information is information indicatingthe kind of DCI format of this downlink control information, i.e.,whether the DCI format is DCI format 0 or DCI format 1A. The informationof localized/distributed VRB assignment flag is information indicating amethod for associating virtual resource blocks indicated by resourceblock assignment information with actual resource blocks (localizedassignment or distributed assignment). The resource block assignmentinformation is information indicating virtual resource blocks allocatedto a PDSCH. The modulation and coding scheme information is informationrelated to a modulation scheme and coding rate of the PDSCH, and theamount of downlink data transmitted by the PDSCH. The HARQ processnumber information is information indicating which number of HARQprocess downlink data transmitted by the PDSCH to which DCI format 1Acorresponds corresponds to. The NDI information is informationindicating whether the PDSCH is initially transmitted or retransmitted.The redundancy version information is information indicating which partof a bit sequence in which the downlink data is coded is transmitted.The transmission power control command for a PUCCH is information usedfor the transmission power control of the PUCCH. The padding bit (0padding) information is a bit inserted so that the sizes of DCI format 0and DCI format 1A are made the same, and the value of the bit is set at“0”.

Since a DCI format used for group scheduling for a plurality of mobilestation apparatuses needs to be received by the plurality of mobilestation apparatuses, the DCI format is assigned in a common search space(CSS). The CSS is a search space in which all the mobile stationapparatuses try to search (detect) a PDCCH. Here, a PDCCH addressed to acertain mobile station apparatus is assigned in a user equipmentspecific search space (USS) and a common search space (CSS). The USS isa search space in which the certain mobile station apparatus tries tosearch (detect) the PDCCH.

The base station apparatus assigns a sequence in which a CRC codegenerated based on a DCI is scrambled by an RNTI (Radio NetworkTemporary Identifier) to the DCI, and transmits the resultant to themobile station apparatus. The mobile station apparatus changes theinterpretation of a DCI in accordance with by what RNTI a CRC code isscrambled. For example, the mobile station apparatus determines that aDCI is a DCI addressed to its own apparatus, when a CRC code isscrambled by a C-RNTI (Cell-RNTI) or an SPS (Semi Persistent Scheduling)C-RNTI allocated from the base station apparatus.

PDCCHs are separately coded (separate coding) for each mobile stationapparatus or for each type. That is, the mobile station apparatusdetects the plurality of PDCCHs, and obtains downlink resourceallocation, uplink resource allocation, and the other controlinformation. The value of a CRC scrambled by an RNTI is assigned to eachPDCCH, and the mobile station apparatus performs descrambling (releaseof scrambling) of the CRC scrambled by the RNTI on the corresponding setof CCEs that may constitute each PDCCH, and obtains the value of theCRC. Then, the mobile station apparatus performs CRC by using the valueof the obtained CRC, and obtains a PDCCH succeeding in the CRC as aPDCCH for its own apparatus. When the descrambling of the CRC scrambledby an RNTI allocated to another apparatus is performed by using an RNTIallocated to its own apparatus, since it is impossible to obtain thevalue of a correct CRC, recognition as a PDCCH addressed to its ownapparatus is not performed. This is also referred to as blind detection,and the range of the set of CCEs on which the mobile station apparatusmay perform blind detection is referred to as a search space. That is,the mobile station apparatus performs blind detection on CCEs in asearch space, and detects a PDCCH addressed to its own apparatus.

The physical downlink shared channel is a channel used to transmitdownlink data (also referred to as DL-SCH: Downlink-Shared Channel), orpaging information.

The downlink reference signal is transmitted from the base stationapparatus to the mobile station apparatus by utilizing a downlink. Themobile station apparatus measures a downlink reference signal, and thus,determines the reception quality of the downlink. Reception quality isnotified to the base station apparatus by using a PUCCH or a PUSCH as achannel quality indicator (CQI) that is a quality information indicator.The base station apparatus performs downlink transmission scheduling forthe mobile station apparatus based on a CQI notified from the mobilestation apparatus. As reception quality, it is possible to usesignal-to-interference ratio (SIR), signal-to-interference plus noiseratio (SINR), signal-to-noise ratio (SNR), carrier-to-interference ratio(CIR), block error rate, (BLER), pathloss (PL), or the like.

The physical uplink shared channel is a channel used to mainly transmituplink data (UL-SCH: Uplink-Shared Channel). When the base stationapparatus performs scheduling for the mobile station apparatus, channelstate information (a downlink channel quality indicator (CQI), aprecoding matrix indicator (PMI), and a rank indicator (RI)), and HARQacknowledgement (ACK)/negative acknowledgement (NACK) for downlinktransmission are also transmitted by using a PUSCH. Here, the uplinkdata (UL-SCH) represents, for example, the transmission of user data,and the UL-SCH is a transport channel. The UL-SCH supports HARQ anddynamic adaptive radio link control, and furthermore, enables beamforming to be utilized. The UL-SCH supports dynamic resource allocationand semi-static resource allocation.

The physical uplink control channel is a channel used to transmit uplinkcontrol information (UCI). Here, the UCI (also referred to as controldata) includes, for example, channel state information (a CQI, PMI, andRI) transmitted (fed back) from the mobile station apparatus to the basestation apparatus, scheduling request (SR) that requests (requeststransmission on an UL-SCH) resource allocation for the mobile stationapparatus to transmit uplink data, HARQ ACK/NACK for downlinktransmission, and the like.

The uplink reference signal is transmitted from the mobile stationapparatus to the base station apparatus. The UL-RS includes a soundingreference signal (SRS) and a demodulation reference signal (DM-RS). TheSRS that is a reference signal for channel estimation is measured by thebase station apparatus and thus is used for determining the receptionquality of an uplink radio transmission signal of the mobile stationapparatus and for the scheduling of the uplink or the adjustment ofuplink timing synchronization based on reception quality. Furthermore,the DM-RS is transmitted together with a PUSCH or a PUCCH, and is usedalso as a reference signal for: calculating the change amount of theamplitude, phase, and frequency of the signal of the PUSCH or the PUCCH;and demodulating the signal transmitted by utilizing the PUSCH or thePUCCH.

Although the transmission bandwidth of the DM-RS accords with thetransmission bandwidth of the PUSCH or the PUCCH, the transmissionbandwidth of the SRS is set independently from that of the DM-RS. Thatis, the transmission bandwidth of the SRS does not necessarily accordwith the transmission bandwidth of the PUSCH or the PUCCH, and is presetby the base station apparatus. Furthermore, frequency hopping is appliedto the SRS for the time axis direction. In the SRS, a frequencydiversity effect and an averaging effect of interference are obtained byusing frequency hopping. Furthermore, in the SRS, the distributionassignment (also referred to as Transmission Comb) of radio resources isperformed in the frequency axis direction. For example, radio resourcescan be assigned at every second subcarrier in the frequency axisdirection, and a plurality of mobile station apparatuses can performfrequency division multiple access (FDMA) of SRSs at the sametransmission timing by changing the position of combs (for example, acomb 0 and a comb 1) to perform assignment. Such FDMA is also referredas interleaved frequency division multiple access (IFDMA).

The A-SRS is a reference signal for channel estimation transmitted whenthe base station apparatus requests transmission of A-SRS for a certainmobile station apparatus. And a subframe for transmitting an A-SRS maybe set by using a PDCCH. Or a subframe for transmitting an A-SRS may beset by using a radio resource control signal, by the base stationapparatus. Furthermore, the subframe for transmitting an A-SRS may beset by using a broadcast channel by the base station apparatus. Here,the radio resource control signal is transmitted at about 100 ms to 200ms intervals, for example.

Furthermore, the P-SRS is a reference signal for channel estimationtransmitted in accordance with a transmission period that the basestation apparatus presets, and a subframe for transmitting a P-SRS maybe set by using a radio resource control signal, or may be set by usinga broadcast channel, by the base station apparatus. Furthermore, settinginformation (SRS configuration) related to SRS parameters such as eachtransmission period and transmission bandwidth of the A-SRS and theP-SRS may be preset and included in a radio resource control signal inthe base station apparatus, and thereafter, may be transmitted to themobile station apparatus.

Furthermore, SRS subframes (respective subframes for transmitting anA-SRS and a P-SRS) that are subframes transmitting SRSs may be set foreach cell or may be set for each mobile station apparatus. The subframesfor transmitting an A-SRS and a P-SRS may be transmitted by using thesame subframe or may be transmitted by using different subframes. Forexample, the base station apparatus may set a subframe for transmittingan A-SRS for each mobile station apparatus, or may set a subframe fortransmitting a P-SRS for each cell. Here, the SRS subframe set for eachcell is referred to as a cell-specific SRS subframe, and the SRSsubframe set for each mobile station apparatus is referred to as amobile station apparatus-specific SRS subframe. Furthermore, as adifferent example, the base station apparatus may set a subframe fortransmitting a P-SRS for each cell, and may set a part of the subframefor transmitting a P-SRS as a subframe for transmitting an A-SRS foreach cell or for each mobile station apparatus.

Furthermore, in A-SRSs, there are an inband A-SRS assigned by utilizinga PUSCH resource and an outband A-SRS in which the parameters of atransmission bandwidth, and the like are set independently from thePUSCH (i.e., which is set by the SRS configuration information describedabove). The inband A-SRS is also referred to as a first A-SRS, and whenan indication of transmission of the first A-SRS is included in anuplink grant, the inband A-SRS is transmitted to the base stationapparatus always together with a PUSCH. That is, the first A-SRS isalways transmitted on the same subframe as the PUSCH. The first A-SRScan improve communication properties in a cell edge, or the like inwhich communication environment is poor.

That is, the base station apparatus transmits resource allocationinformation for a PUSCH and an uplink grant including an indication oftransmission of the first A-SRS to the mobile station apparatus, and themobile station apparatus assigns the first A-SRS in a PUSCH resourceallocated by the base station apparatus and transmits the first A-SRS tothe base station apparatus.

The outband A-SRS is also referred to as a second A-SRS, the parametersof a transmission bandwidth, and the like are set independently from thePUSCH as in the P-SRS, and the outband A-SRS does not necessarily needto be transmitted to the base station apparatus together with a PUSCH.Since the second A-SRS can be transmitted independently from the PUSCH,the second A-SRS can be assigned in a frequency band different from afrequency band in which a PUSCH is assigned, and can be used for dynamicfrequency selection scheduling.

That is, The base station apparatus sets, to the mobile stationapparatus, parameters (for example, a transmission bandwidth, aresource, and the like) for the mobile station apparatus to transmit thesecond A-SRS. The base station apparatus transmits an uplink grantincluding an indication of transmission of the second A-SRS to themobile station apparatus, and the mobile station apparatus assigns thesecond A-SRS in a resource set by the base station apparatus andtransmits the second A-SRS to the base station apparatus. That is, themobile station apparatus assigns the second A-SRS in a resourcedifferent from a PUSCH resource allocated by an uplink grant from thebase station apparatus and transmits the second A-SRS to the basestation apparatus. The base station apparatus sets, independently from aPUSCH resource, a resource to which the mobile station apparatus assignsthe second A-SRS.

FIGS. 8(a) and 8(b) are views showing schematic configurations of aninband A-SRS (a first A-SRS) and an outband A-SRS (a second A-SRS). FIG.8 (a) shows a schematic structure of the first A-SRS. The first A-SRS isset at, for example, the same transmission bandwidth as a PUSCH and isincluded in a PUSCH resource. Furthermore, the first A-SRS istransmitted to the base station apparatus always together with a PUSCH.When the first A-SRS and a P-SRS are transmitted at the same timing,they may be set so as to be assigned in different combs in advance andto be transmitted at the same timing, and the first A-SRS may betransmitted at certain timing different from a P-SRS transmissiontiming. That is, since the symbol in which the first A-SRS is assigneddoes not necessarily need to be an SRS symbol, the symbol in which thefirst A-SRS is assigned may be any of symbols in which PUCCHs areassigned. Here, the symbol in which the first A-SRS is assigned may beuniquely predetermined in the system, may be notified from the basestation apparatus to the mobile station apparatuses as broadcastinformation at a time, or may be notified from the base stationapparatus to individual mobile station apparatuses.

FIG. 8(b) shows a schematic configuration of the second A-SRS. Thesecond A-SRS is different from the first A-SRS, and parameters are setindependently from the PUSCH. Therefore, it is possible to set a widetransmission bandwidth necessary to perform frequency selectionscheduling. Furthermore, since the second A-SRS can be assignedindependently from the PUSCH (in a different resource), the second A-SRSdoes not necessarily need to be transmitted by the same subframe as aPUSCH. That is, since the mobile station apparatus 3 may transmit thesecond A-SRS to the base station apparatus without the PUSCH (UL-SCHdata), the base station apparatus can allocate, by scheduling, a PUSCHresource to another mobile station apparatus that does not transmit thesecond A-SRS, and spectrum efficiency can be improved in the entiresystem. When a P-SRS and the second A-SRS are transmitted at the sametiming, the mobile station apparatus 3 may transmits the second A-SRS tothe base station apparatus 1. Furthermore, when a P-SRS and the secondA-SRS are transmitted at the same timing, the mobile station apparatus 3may transmits the P-SRS to the base station apparatus 1. Furthermore,the mobile station apparatus 3 may be performed so that the P-SRS andthe second A-SRS are transmitted at the same timing by setting differentcombs. Here, the same timing also means that transmission timing is thesame symbol.

The physical random access channel is a physical channel used totransmit a random access preamble, and has a guard time. It is thebiggest goal of the PRACH that the mobile station apparatus issynchronized with the base station apparatus, and in addition to that,the PRACH is used for an initial access, a handover, a reconnectionrequest, and a scheduling request.

The scheduling request is information for the mobile station apparatusto request PUSCH resource allocation from the base station apparatus.The mobile station apparatus, when information data transmitted to abuffer of its own apparatus is accumulated and PUSCH resource allocationis requested, transmits an SR. Furthermore, the mobile station apparatustransmits an SR to the base station apparatus by using a PUSCH allocatedin advance by the base station apparatus. The base station apparatusallocates periodic resources for the mobile station apparatus to assignan SR, at the start of communication connection with the mobile stationapparatus.

(SRS Resource Allocation and Frequency Hopping)

FIG. 9 is a view showing a schematic structure of SRS resourceallocation and frequency hopping (FH). In FIG. 9, the horizontal axisrepresents time and the vertical axis represents frequency. The leftside in FIG. 9 shows an example of SRS resource allocation. In theexample on the left side in FIG. 9, 14 symbols are arrayed in the timeaxis direction. 7 symbols correspond to one slot, and the length of oneslot is 0.5 milliseconds (ms). Furthermore, 14 symbols (that correspondto two slots) correspond to one subframe, and the length of one subframeis 1 millisecond (ms). In this way, in an uplink signal in which onesubframe is composed of 14 symbols, an SRS is assigned in the fourteenthsymbol (also referred to as an SRS symbol). The SRS resource assigned inthe fourteenth symbol (the bandwidth in the frequency axis direction) isset in the base station apparatus in accordance with an uplink systembandwidth or the transmission power of the mobile station apparatus.Furthermore, the PRACH can change and allocate the bandwidth and thetime symbol length in accordance with the kind of message to transmit ora format. When one subframe is composed of 14 symbols, DM-RSs areassigned in the fourth and eleventh symbols (also referred to as DM-RSsymbols), and the transmission bandwidth of the DM-RS accords with thetransmission bandwidth of a PUSCH.

Furthermore, frequency hopping that changes frequency position for eachtransmission is applied in the time axis direction. The right side inFIG. 9 shows one example of SRS frequency hopping. Although an SRS istransmitted for each transmission period T on the right side in FIG. 9,hopping is performed in the frequency axis direction for each period T(i.e., for each SRS transmission) as shown in FIG. 9. When a hoppingbandwidth that is one piece of SRS configuration information is set at abandwidth wider than an SRS transmission bandwidth, the mobile stationapparatus can apply frequency hopping.

[Structure of a Base Station Apparatus]

FIG. 1 is a block diagram showing a schematic functional structure of abase station apparatus 1 of the present invention. The base stationapparatus 1 includes a transmission unit 101, a reception unit 103, ascheduling unit (base station side scheduling unit) 105, a higher layers107, a channel estimation unit 108, and an antenna 109. The transmissionunit 101 includes a data control unit 1011, a modulation unit 1013, anda radio transmission unit 1015. Furthermore, the transmission unit 103includes a radio reception unit 1031, a demodulation unit 1033, and adata extraction unit 1035.

The data control unit 1011 allows user data and control data to beinput, assigns the control data to a PDCCH by an indication from thescheduling unit 105, and assigns transmission data and the control datafor a mobile station apparatus 3 to a PDSCH. The modulation unit 1013performs signal processing such as data modulation, serial/paralleltransform of an input signal, IFFT, CP insertion, filtering, and thelike, and generates a transmission signal. The radio unit 1015, afterup-converting modulated data into a radio frequency, transmits theresultant to the mobile station apparatus 3 via the antenna 109.Furthermore, the transmission unit 101 causes first to third controlinformation to be included in the PDCCH by an indication of thescheduling unit 105, and transmits the PDCCH to the mobile stationapparatus 3.

The radio reception unit 1031 receives an uplink signal from the mobilestation apparatus 3, down-converts the uplink signal into a basebandsignal, and outputs the received data to the demodulation unit 1033. Thedata extraction unit 1035 checks the accuracy of the received data andnotifies the scheduling unit 105 of the check result. When the receiveddata is correct, the data extraction unit 1035 separates the receiveddata into user data and control data. The data extraction unit 1035outputs Layer 2 control data such as downlink channel quality indicationinformation, acknowledgement/negative acknowledgement (ACK/NACK) ofdownlink data, and the like, of the control data to the scheduling unit105, and outputs other control data of Layer 3 and the like and userdata, to the higher layers 107. When the received data is incorrect, thedata extraction unit 1035 saves the received data in order to synthesizethe received data with data to be retransmitted, and performs synthesisprocessing when the data to be retransmitted is received.

The scheduling unit 105 performs scheduling for assigning user data andcontrol data in a PDSCH and a PDCCH. Furthermore, the scheduling unit105 indicates the transmission unit 101 to transmit the PDCCH (DCIformat) including an indication of transmission of an A-SRS by anindication from the higher layers 107.

The higher layers 107 performs processing of a medium access control(MAC) layer, a radio link control (RLC) layer, a packet data convergenceprotocol (PDCP) layer, and a radio resource control (RRC) layer. Sincethe higher layers 107 controls processing units of the lower layerintegrally, interfaces between: the higher layers 107; and thescheduling unit 105, the channel estimation unit 108, the antenna 109,the transmission unit 101, and the reception unit 103 are present.

The higher layers 107 has a radio resource control unit 1071 (alsoreferred to as a control unit). Furthermore, the radio resource controlunit 1071 performs management of various types of setting information,management of system information, paging control, management of acommunication state of each mobile station apparatus, mobilitymanagement of a handover and the like, management of a buffer situationfor each mobile station apparatus, management of connection setting ofunicast and multicast bearers, management of a mobile station identifier(also referred to as a UEID, or an RNTI (Radio Network TemporaryIdentifier)), and the like. Furthermore, the higher layers 107 performstransmission/reception of information to/from another base stationapparatus 1 and to/from an higher node. Furthermore, the higher layers107 performs setting and management of parameters such as thetransmission bandwidth of an SRS, and the like as SRS configurationinformation, and indicates the scheduling unit 105 to notify the mobilestation apparatus 3 of a radio resource control signal including SRSconfiguration information. Furthermore, the SRS configurationinformation may include not only a P-SRS parameter, but also A-SRS (eachof the first A-SRS and the second A-SRS) parameters to be notified.Furthermore, when the higher layers 107, if necessary, wants to performuplink channel estimation, the higher layers 107 indicates thescheduling unit 105 on the transmission of an A-SRS. Furthermore, thehigher layers 107 determines the communication environment of the mobilestation apparatus 3 based on the channel estimation value of an uplinksignal obtained by the channel estimation unit 108, and performs optimalPUSCH resource allocation. Furthermore, in view of the communicationenvironment of the mobile station apparatus 3, the higher layers 107 canindicate the mobile station apparatus 3 to perform optimal A-SRStransmission. In order to indicate the mobile station apparatus 3 toperform transmission switching of the first A-SRS utilizing a PUSCHresource and the second A-SRS in which parameters and the like are setindependently from a PUSCH, scheduling information including informationfor performing indication of the transmission switching of the firstA-SRS and the second A-SRS is output to the scheduling unit 105.

Furthermore, in uplink scheduling, the scheduling unit 105 generatesscheduling information used in: processing of selecting an uplinktransport format (a transmission format, i.e., physical resource blockallocation, a modulation scheme, a coding scheme, and the like) formodulating each data piece; and the uplink scheduling, based on: anestimation result of an uplink channel state (radio channel state) thatthe channel estimation unit 108 outputs; a resource allocation requestfrom the mobile station apparatus 3; available PRB information of themobile station apparatus 3; scheduling information input from the higherlayers 107; and the like. This scheduling information used in the uplinkscheduling is output to the data control unit 1011. Furthermore, when anindication of transmission of the first or second A-SRS is performedfrom the higher layers 107, the scheduling information is reset, and theresultant is output to the data control unit 1011.

Furthermore, the scheduling unit 105 maps a logical channel of thedownlink input from the higher layers 107 to a transport channel, andoutputs the resultant to the data control unit 1011. Furthermore, afterthe scheduling unit 105, if necessary, processes control data and atransport channel obtained in the uplink that are input from the dataextraction unit 1035, the scheduling unit 105 maps the resultant to alogical channel of the uplink, and outputs the resultant to the higherlayers 107.

The channel estimation unit 108 estimates an uplink channel state from ademodulation reference signal for demodulation of uplink data, andoutputs the estimation result to the demodulation unit 1033.Furthermore, in order to perform uplink scheduling, the channelestimation unit 108 estimates an uplink channel state from a soundingreference signal, and outputs the estimation result to the demodulationunit 105.

[Structure of a Mobile Station Apparatus]

FIG. 2 is a block diagram showing a schematic functional configurationof a mobile station apparatus 3 of the present invention. The basestation apparatus 3 includes a transmission unit 201, a reception unit203, a scheduling unit 205, a reference signal generation unit 206,higher layers 207, and an antenna 209. The transmission unit 201includes a data control unit 2011, a modulation unit 2013, and a radiotransmission unit 2015. Furthermore, the transmission unit 203 includesa radio reception unit 2031, a demodulation unit 2033, and a dataextraction unit 2035.

User data and control data are input from the higher layers 207 to thedata control unit 2011. The data control unit 2011 assigns the inputdata in a PUSCH and a PUCCH by an indication from the scheduling unit205. The modulation unit 2013 performs data modulation of the PUSCH andthe PUCCH, and outputs the resultant to the radio transmission unit2015. The radio transmission unit 2015: performs signal processing suchas discrete Fourier transform (DFT), subcarrier mapping, inverse fastFourier transform (IFFT), cyclic prefix (CP) insertion, and filtering,on the modulated data; generates a transmission signal; up-converts thetransmission signal into a radio frequency; and thereafter, transmitsthe resultant to the base station apparatus 1 via the antenna 209.

The radio reception unit 2031 receives a downlink signal from the basestation apparatus 1, down-converts the downlink signal into a basebandsignal, and outputs the received signal to the demodulation unit 2033.The demodulation unit 2033 demodulated received data. The dataextraction unit 2035 separates the received data into user data andcontrol data. Furthermore, the data extraction unit 2035 outputsscheduling information, random access response message, the control datarelated to discontinuous reception control, and other 2 Layer controldata to the scheduling unit 205, and outputs the user data to the higherlayers 207. Furthermore, the data extraction unit 2035 detects the codepoint of control information included in a PDCCH (DCI format) andoutputs the code point to the higher layers 207.

The scheduling unit 205 analyzes the control data output from the dataextraction unit 2035, generates uplink scheduling information, andindicates the data control unit 2011 to allocate user data and controldata to a PUSCH and a PUCCH based on the scheduling information.

Furthermore, the scheduling unit 205 includes a reference signal controlunit 2051. The reference signal control unit 2051 extracts SRSconfiguration information based on scheduling information transmittedfrom the base station apparatus 1. Furthermore, the reference signalcontrol unit 2051 performs transmission control when an SRS, and a PUSCHand/or a PUCCH are generated at the same timing, and generates SRStransmission control information. The reference signal control unit 2051outputs the SRS configuration information and the SRS transmissioncontrol information to the reference signal generation unit 206. Here,the SRS configuration information is information for setting parameterssuch as an SRS transmission bandwidth, and a transmission period. TheSRS transmission control information is information indicating an SRStransmission control method when an SRS and other uplink channels (aPUSCH and/or a PUCCH) are allocated at the same subframe. For example,when an SRS and a PUCCH are generated in the same subframe, the SRStransmission control information is information for indicating themobile station apparatus 3 to perform processing that the SRS is nottransmitted.

In uplink scheduling, the scheduling unit 205 generates schedulinginformation used in: scheduling processing for mapping, to a transportchannel, a logical channel of the uplink input from the higher layers207; and the uplink scheduling, based on: a buffer situation of theuplink input from the higher layers 207; uplink scheduling informationfrom the base station apparatus 1 that is input from the data extractionunit 2035 (a transport format, HARQ retransmission information, and thelike); scheduling information input from the higher layers 207; and thelike. About the uplink transport format, information notified from thebase station apparatus 1 is utilized. This scheduling information isoutput to the data control unit 2011.

Furthermore, the scheduling unit 205 maps a logical channel of theuplink input from the higher layers 207 to a transport channel, andoutputs the resultant to the data control unit 2011. Furthermore, thescheduling unit 205 outputs also a CSI, CQI, PMI, and RI input from thechannel estimation unit 208, and a CRC check result input from the dataextraction unit 2035 to the data control unit 2011. Furthermore, afterthe scheduling unit 205, if necessary, processes control data and atransport channel obtained in the downlink that are input from the dataextraction unit 2035, the scheduling unit 205 maps the resultant to alogical channel of the downlink, and outputs the resultant to the higherlayers 207.

The channel estimation unit 208 estimates a downlink channel state froma DL-RS for the demodulation of downlink data, and outputs theestimation result to the demodulation unit 2033. Furthermore, thechannel estimation unit 208 estimates a downlink channel state from adownlink reference signal in order to notify the base station apparatus1 of the estimation result of the downlink channel state (a radiochannel state, CSI, CQI, PMI, and RI), and outputs this estimationresult to the scheduling unit 205 as a CSI, CQI, PMI, and RI, forexample.

The reference signal generation unit 206 generates an SRS (A-SRS, andP-SRS) based on SRS configuration information and SRS transmissioncontrol information input from the reference signal control unit 2051,and outputs the resultant to the radio transmission unit 2015.

The higher layers 207 performs processing of a medium access control(MAC) layer, a radio link control (RLC) layer, a packet data convergenceprotocol (PDCP) layer, and a radio resource control (RRC) layer. Sincethe higher layers 207 controls processing units of the lower layerintegrally, interfaces between: the higher layers 207; and thescheduling unit 205, the channel estimation unit 208, the antenna 209,the transmission unit 201, and the reception unit 203 are present(however, not shown).

The higher layers 207 includes a radio resource control unit 2071 (alsoreferred to as a control unit). The radio resource control unit 2071performs management of various types of configuration information,management of system information, paging control, management of acommunication state of its own station, mobility management of ahandover and the like, management of a buffer situation, management ofconnection setting of unicast and multicast bearers, and management of amobile station identity (UEID). Furthermore, the higher layers 207extracts SRS configuration information from a radio resource controlsignal transmitted from the base station apparatus 1, and sets SRSparameters. Furthermore, when an indication of transmission of an A-SRSis included in a received DCI format, scheduling information in whichthe transmission of an A-SRS is taken into account is reset, and isoutput the reset scheduling information to the scheduling unit 205.Furthermore, the higher layers 207 sets the first A-SRS or the secondA-SRS in accordance with the A-SRS transmission indication from the basestation apparatus 1, and outputs the resultant to the scheduling unit205 as scheduling information.

First Embodiment

A first embodiment of the present invention will be described below. Inthe first embodiment, the base station apparatus 1: notifies the mobilestation apparatus 3 of transmission control information for setting, tothe mobile station apparatus 3, whether to transmit a first soundingreference signal assigned in a physical uplink shared channel resourceor to transmit a second sounding reference signal assigned in a resourcedifferent from the physical uplink shared channel resource; and notifiesthe mobile station apparatus 3 of an uplink grant including anindication of transmission of a sounding reference signal. Whenreceiving the indication of transmission of the sounding referencesignal included in the uplink grant, the mobile station apparatus 3transmits the first sounding reference signal to the base stationapparatus 1 when the transmission of the first sounding reference signalis set by the transmission control information, and transmits the secondsounding reference signal to the base station apparatus 1 when thetransmission of the second sounding reference signal is set by thetransmission control information.

In the first embodiment, the base station apparatus 1 determines(controls), by a radio resource control signal (RRC signaling), a radioresource in which an A-SRS is assigned. That is, the base stationapparatus 1 can indicate, by using RRC signaling, the mobile stationapparatus 3 to: assign a first A-SRS in a PUSCH resource allocated by anuplink grant; and transmit it. Furthermore, the base station apparatus 1can indicate, by using RRC signaling, the mobile station apparatus 3 to:assign a second A-SRS in a resource set (independently from the PUSCHresource); and transmit it to the base station apparatus 1. That is, thebase station apparatus 1 can indicate, by using RRC signaling, themobile station apparatus 3 on whether the mobile station apparatus 3assigns an A-SRS in a PUSCH resource and transmits it, or assigns theA-SRS in a resource set (independently from the PUSCH resource), andtransmits it.

For example, the base station apparatus 1 determines (controls), by aradio resource control signal (RRC signaling) in accordance with achange in the communication environment of the mobile station apparatus3, a radio resource in which an A-SRS is assigned. For example, when itis determined that the communication environment of the mobile stationapparatus 3 becomes worse, the base station apparatus 1 can indicate themobile station apparatus 3 to perform transmission of the first A-SRSassigned by utilizing a PUSCH resource; and when it is determined thatthe communication environment of the mobile station apparatus 3 becomesbetter, the base station apparatus 1 can indicate the mobile stationapparatus 3 to transmits the second A-SRS with a wider transmissionbandwidth in which parameters are set independently from the PUSCH.Furthermore, for example, when it is determined that the mobile stationapparatus 3 is in a cell edge, the base station apparatus 1 can indicatethe mobile station apparatus 3 to perform transmission of the firstA-SRS assigned in a PUSCH resource; and when it is determined that themobile station apparatus 3 is at the cell center, the base stationapparatus 1 can indicate the mobile station apparatus 3 to transmits thesecond A-SRS with a wider transmission bandwidth in which parameters areset independently from the PUSCH (which is assigned in a resourcedifferent from the PUSCH). Here, for the mobile station apparatus 3performing communication by using a plurality of unlink componentcarriers, the base station apparatus 1 may be preset, for each unlinkcomponent carrier, which A-SRS is used to perform transmission, or mayset the same A-SRS (any one of the first A-SRS or the second A-SRS) foreach the mobile station apparatus 3.

FIGS. 3(a) and 3(b) are views showing an example of a DCI formatincluding an indication of transmission of an A-SRS in the firstembodiment. The DCI format (uplink grant) illustrated in FIG. 3(a)indicates that the DCI format (uplink grant) includes carrier indicator(CI) information indicating from which uplink component carrier anuplink signal is transmitted (in which component carrier a PUSCHscheduled by the DCI format is assigned), PDCCH format identification(Flag for format 0/format 1A differentiation) information, a frequencyhopping flag, resource block assignment and hopping resource allocationinformation, modulation and coding scheme and redundancy versioninformation, NDI (New Data Indicator) information, information oftransmission power control (TPC) command for the scheduled PUSCH,information of a cyclic shift for a DM-RS, CQI transmission indication(also referred to as a CQI request) information, padding bit (0 padding)information, cyclic redundancy check (CRC) information and informationof the indication of transmission of an A-SRS (SRS activation, an SRSrequest, or a trigger for SRS transmission) (defined so as to give theindication of transmission of an A-SRS, for example represented by onebit).

In FIG. 3(a), when an indication of transmission of an A-SRS is includedin the uplink grant, the mobile station apparatus 3 transmits the firstA-SRS or the second A-SRS to the base station apparatus 1 in accordancewith a radio resource control signal notified from the base stationapparatus 1. That is, when the field defined for the indication oftransmission of an A-SRS included in the uplink grant is set at apredetermined value (for example, “1”), the mobile station apparatus 3transmits an A-SRS to the base station apparatus 1 in a certainsubframe.

FIG. 3(b) shows an A-SRS transmission indication method when A-SRStransmission indication information is not included in the DCI format.In FIG. 3(b), when the frequency hopping flag and the padding bitinformation each are a predetermined code point (predetermined value),the mobile station apparatus 3 recognizes that an indication oftransmission of an A-SRS is notified, and transmits an A-SRS to the basestation apparatus 1.

Furthermore, in FIGS. 3(a) and 3 (b), when the CQI transmissionindication included in the uplink grant is also set (for example, theCQI request is set at “1”), a CQI and an A-SRS are transmitted to thebase station apparatus 1 in the same subframe. Here, the mobile stationapparatus 3 assigns the CQI and UL-SCH data (Uplink Shared Channel data,a transport block for an UL-SCH) in a PUSCH, and transmits them togetherwith the A-SRS to the base station apparatus 1 in the same subframe.

Here, at this time, cyclic shifts applied to the A-SRSs (each of thefirst A-SRS and the second A-SRS) may be the same as that of a P-SRS,may be defined in association with the cyclic shift of a DM-RS, may beuniquely predetermined in the system, may be notified from the basestation apparatus 1 to the mobile station apparatuses 3 as broadcastinformation at a time, or may be notified from the base stationapparatus 1 to individual mobile station apparatuses 3. Furthermore,when the number of times of transmission of the A-SRSs (each of thefirst A-SRS and the second A-SRS) and a transmission timer are preset bythe base station apparatus 1, and the mobile station apparatus 3 isnotified by using a radio resource control signal, or the like, themobile station apparatus 3 transmits A-SRSs to the base stationapparatus 1 until the number of times of transmission and thetransmission timer are expired.

Furthermore, the parameters of the second A-SRS may be the same as thoseof the P-SRS, may be uniquely predetermined in the system, may benotified from the base station apparatus 1 to the mobile stationapparatuses 3 as broadcast information at a time, or may be notifiedfrom the base station apparatus 1 to individual mobile stationapparatuses 3. Respective different cyclic shifts may be applied to thefirst A-SRS and the second A-SRS. For example, the cyclic shift of thefirst A-SRS may be made the same cyclic shift as a DM-RS transmitted inthe same subframe, the cyclic shift of the second A-SRS may be notifiedfrom the base station apparatus 1 to each mobile station apparatus 3 bya radio resource control signal. Furthermore, the cyclic shifts of thefirst A-SRS and the second A-SRS may be associated with parametersapplied to the cyclic shift of a DM-RS (for example, a cyclic shiftindex of the DM-RS, and cyclic shift information of the DM-RS), anddifferent values may be individually applied to the cyclic shifts of thefirst A-SRS and the second A-SRS, or the same value may be applied tothe cyclic shifts of the first A-SRS and the second A-SRS. That is, thebase station apparatus 1 can set the cyclic shift of the first A-SRS andthe cyclic shift of the second A-SRS so as to associate the cyclic shiftof the first A-SRS and the cyclic shift of the second A-SRS withparameters applied to the cyclic shift of the DM-RS, and the mobilestation apparatus 3 can uniformly (mechanically) set the cyclic shiftsapplied to the first A-SRS and the second A-SRS from the parametersapplied to the DM-RS.

Second Embodiment

A second embodiment of the present invention will now be describedbelow. In the second embodiment, when the base station apparatus 1indicates the mobile station apparatus 3 to perform transmission of thefirst sounding reference signal assigned in a physical uplink sharedchannel resource, the base station apparatus 1 sets transmissionindication information included in an uplink grant as a first value; andwhen the base station apparatus 1 indicates the mobile station apparatus3 to perform transmission of the second sounding reference signalassigned in a resource different from the physical uplink shared channelresource, the base station apparatus 1 sets the transmission indicationinformation as a second value. Furthermore, the base station apparatus 1notifies the mobile station apparatus 3 of the uplink grant includingthe transmission indication information set at the first value or thesecond value. When the transmission indication information included inthe uplink grant is the first value, the mobile station apparatus 3transmits the first sounding reference signal to the base stationapparatus 1; and when the transmission indication information includedin the uplink grant is the second value, the mobile station apparatus 3transmits the second sounding reference signal to the base stationapparatus 1.

In the second embodiment, by adding A-SRS transmission indicationinformation configured by a plurality of bits (a bit sequence) not lessthan two bits to a DCI format (uplink grant), in accordance with the bitsequence (a predetermined value) represented by the A-SRS transmissionindication information, it is possible to dynamically switchtransmission of the first A-SRS and the second A-SRS. That is, since thebase station apparatus 1, if necessary, can dynamically control an A-SRStransmission method of the mobile station apparatus 3, and can performoptimal channel estimation, it is possible to perform effectivecommunication between the base station apparatus 1 and the mobilestation apparatus 3.

That is, the base station apparatus 1 can indicate, by using A-SRStransmission indication information, the mobile station apparatus 3 to:assign the first A-SRS in a PUSCH resource allocated by an uplink grant;and transmit it. Furthermore, the base station apparatus 1 can indicate,by using A-SRS transmission indication information, the mobile stationapparatus 3 to: assign the second A-SRS in a resource set (independentlyfrom the PUSCH resource); and transmit it to the base station apparatus1. That is, the base station apparatus 1 can indicate, by using A-SRStransmission indication information, the mobile station apparatus 3 onwhether the mobile station apparatus 3 assigns an A-SRS in a PUSCHresource and transmits it, or assigns the A-SRS in a resource set(independently from the PUSCH resource) and transmits it.

FIGS. 4(a) and 4(b) are views showing an example of a DCI formatincluding an indication of transmission of an A-SRS in the secondembodiment. Although the DCI format illustrated in FIG. 4(a) is the samein configuration as the DCI format illustrated in FIG. 3(a), A-SRStransmission indication information is configured by a plurality of bitsnot less than two bits. A-SRS transmission indication information isconfigured by a plurality of bits not less than two bits, and thus, itis possible to dynamically switch indication of transmission of thefirst A-SRS and the second A-SRS.

FIG. 4(a) shows a structure of control information when A-SRStransmission indication (SRS activation) information is added to the DCIformat. For example, the A-SRS transmission indication information isconfigured by two bits, “00” represents the stop of transmission of anA-SRS, “01” represents a first A-SRS transmission, and “10” represents asecond A-SRS transmission. Furthermore, as in FIG. 4(b), when the A-SRStransmission indication information is “11”, control informationincluded in the DCI format is recognized as different controlinformation from the control information shown in FIG. 4(a). Forexample, control information other than A-SRS transmission indicationinformation is recognized as setting information (SRS configurations forthe 2nd A-SRS) giving indication of the parameters of the second A-SRSsuch as the transmission bandwidth and the cyclic shift of the secondA-SRS. Because of this, it is possible to perform setting so as totransmit the second A-SRS in which the parameters based on the settinginformation are set. The mobile station apparatus 3 can dynamicallyswitch the first A-SRS and the second A-SRS, and perform. A-SRStransmission. Here, a transmission bandwidth (SRS transmissionbandwidth) when the mobile station apparatus 3 transmits the secondA-SRS is included in the parameters (SRS configurations for the 2ndA-SRS) of the second A-SRS included in the setting information.Furthermore, a cyclic shift used in order to maintain the orthogonalitybetween the mobile station apparatuses 3 or between signals is includedin the parameters of the second A-SRS. Furthermore, informationindicating a frequency position at which the second A-SRS is assigned isincluded in the parameters of the second A-SRS. Furthermore, the numberof times of transmission or a transmission stop time for expiringtransmission of the second A-SRS are included in the parameters of thesecond A-SRS. Furthermore, an antenna port (antenna index) fortransmitting the second A-SRS is included in the parameters of thesecond A-SRS. Furthermore, a multiple-antenna simultaneous transmissionflag indicating whether or not to perform transmission of an A-SRS bysimultaneously using multiple antennas as in MIMO is included in theparameters of the second A-SRS. Furthermore, a TPC command (transmissionpower control information) for the second A-SRS is included in theparameters of the second A-SRS. Furthermore, which parameter of theseparameters of the second A-SRS is used may be uniquely predetermined inthe system, may be notified from the base station apparatus 1 to themobile station apparatuses 3 as broadcast information at a time, or maybe notified from the base station apparatus 1 to individual mobilestation apparatuses 3.

Third Embodiment

A third embodiment of the present invention will now be described below.In the third embodiment, when the base station apparatus 1 indicates themobile station apparatus 3 to perform transmission of the first soundingreference signal assigned in a physical uplink shared channel resource,the base station apparatus 1 sets transmission indication information ofone bit included in an uplink grant at a predetermined value; and whenthe base station apparatus 1 indicates the mobile station apparatus 3 toperform transmission of the second sounding reference signal assigned ina resource different from the physical uplink shared channel resource,the base station apparatus 1 sets first control information included inthe uplink grant at a predetermined code point. Furthermore, the basestation apparatus 1 sets the indication of transmission of a soundingreference signal with the transmission indication information or thefirst control information, notifies the mobile station apparatus 3 ofthe uplink grant including the transmission indication information setat the predetermined value or the first control information set at thepredetermined code point, and thus, notifies the mobile stationapparatus 3 of the uplink grant including the indication of transmissionof a sounding reference signal. When the transmission indicationinformation included in the uplink grant indicates the indication oftransmission of a sounding reference signal, the mobile stationapparatus 3 transmits the first sounding reference signal to the basestation apparatus 1; and when the first control information included inthe uplink grant is a predetermined code point, the mobile stationapparatus 3 transmits the second sounding reference signal to the basestation apparatus 1.

In the third embodiment, the base station apparatus 1 notifies themobile station apparatus 3 of an indication of transmission of the firstA-SRS by transmission indication information of one bit (SRS activationfor the 1st A-SRS), and notifies the mobile station apparatus 3 of anindication of transmission of the second A-SRS by the first controlinformation that is a predetermined code point. That is, the basestation apparatus 1 can indicate, by using transmission indicationinformation of one bit, the mobile station apparatus 3 to: assign thefirst A-SRS in a PUSCH resource allocated by an uplink grant; andtransmit it. Furthermore, the base station apparatus 1 can indicate, byusing the first control information that is a predetermined code point(predetermined control information set at a predetermined value), themobile station apparatus 3 to: assign the second A-SRS in a resource set(independently from the PUSCH resource); and transmit it to the basestation apparatus 1. Here, it is predefined by specifications and thelike that what control information included in a DCI format (uplinkgrant) is set at predetermined control information (the first controlinformation), and an indication of transmission of the second A-SRS isperformed by the base station apparatus 1 in accordance with at whatvalue the predetermined control information is set.

Here, when the transmission of the second A-SRS is notified by the firstcontrol information, control information fields other than the firstcontrol information may be used for indicating other controlinformation. For example, the base station apparatus 1 can performallocation to the mobile station apparatus 3 as a parameter of thesecond A-SRS in the control information field other than the firstcontrol information. A transmission bandwidth (SRS transmissionbandwidth) when the mobile station apparatus 3 transmits the secondA-SRS is included in the parameter of the second A-SRS (SRSconfigurations for the 2nd A-SRS). Furthermore, a cyclic shift used inorder to maintain the orthogonality between the mobile stationapparatuses 3 or between signals is included in parameters of the secondA-SRS. Furthermore, information indicating a frequency position at whichthe second A-SRS is assigned is included in the parameters of the secondA-SRS. Furthermore, the number of times of transmission or atransmission stop time for expiring transmission of the second A-SRS areincluded in the parameters of the second A-SRS. Furthermore, an antennaport (antenna index) for transmitting the second A-SRS is included inthe parameters of the second A-SRS. Furthermore, a multiple-antennasimultaneous transmission flag indicating whether or not to performtransmission of the second A-SRS by simultaneously using multipleantennas as in MIMO is included in the parameters of the second A-SRS.Furthermore, a TPC command (transmission power control information) forthe second A-SRS is included in the parameters of the second A-SRS.Furthermore, which parameter of these parameters of the second A-SRS isused may be uniquely predetermined in the system, may be notified fromthe base station apparatus 1 to the mobile station apparatuses 3 asbroadcast information at a time, or may be notified from the basestation apparatus 1 to individual mobile station apparatuses 3.

In the third embodiment, in accordance with the communicationenvironment of the mobile station apparatus 3, the base stationapparatus 1 can dynamically change parameters such as the transmissionbandwidth, transmission timing, and cyclic shift of the second A-SRS,can reduce interference in the other mobile station apparatuses 3, canperform flexible SRS assignment, and can perform improve communicationquality.

Furthermore, by controlling the indication of transmission of the secondA-SRS by using the first control information that is a predeterminedcode point with little false detection, it is possible to reduce theunnecessary transmission of the second A-SRS, and to reduce the effectof interference in the SRSs of the other mobile station apparatuses 3due to the false transmission of the second A-SRS.

FIGS. 5(a) and 5(b) are views showing an example of a DCI formatincluding an indication of transmission of an A-SRS in the thirdembodiment. The DCI format (uplink grant) illustrated in FIG. 5 (a)indicates that the DCI format (uplink grant) includes carrier indicator(CI) information indicating from which uplink component carrier anuplink signal is transmitted (in which uplink component carrier a PUSCHscheduled by the DCI format is assigned), PDCCH format identification(Flag for format 0/format 1A differentiation) information, a frequencyhopping flag, resource block assignment and hopping resource allocationinformation, modulation and coding scheme and redundancy versioninformation, NDI (New Data Indicator) information, information oftransmission power control (TPC) command for the scheduled PUSCH,information of a cyclic shift for a DM-RS, CQI transmission indication(also referred to as CQI request) information, padding bit (0 padding)information, cyclic redundancy check (CRC) information and informationof the indication of transmission of an A-SRS (SRS activation, an SRSrequest, or a trigger for SRS transmission) (defined so as to give theindication of transmission of an A-SRS, for example represented by onebit).

In FIG. 5(a), when the indication of transmission of an A-SRS is set,the mobile station apparatus 3 transmits a PUSCH and an A-SRS to thebase station apparatus 1 in the same subframe. That is, when the fielddefined for the indication of transmission of an A-SRS that is includedin the uplink grant is set at for example, “1”, the mobile stationapparatus 3 transmits both the PUSCH and the A-SRS to the base stationapparatus 1 in a certain subframe. Furthermore, at this time, when anindication of transmission of a CQI included in the uplink grant is alsoset (for example, the CQI request is set at “1”), a CQI and the A-SRSare transmitted to the base station apparatus 1 in the same subframe.Here, the mobile station apparatus 3 assigns the CQI and UL-SCH data(Uplink Shared Channel data, a transport block for an UL-SCH) in thePUSCH, and transmits them together with the A-SRS to the base stationapparatus 1 in the same subframe.

Furthermore, at this time, the base station apparatus 1 can indicate themobile station apparatus 3 to perform transmission of only a CQI(transmission of a CQI without UL-SCH data, and transmission of onlyuplink control information). For example, the base station apparatus 1can instruct the mobile station apparatus 3 to perform transmission ofonly a CQI by setting the predetermined information of an uplink grantat a predetermined value (at a predetermined code point). For example,the base station apparatus 1 can instruct the mobile station apparatus 3to perform transmission of only a CQI by setting the resource blockassignment, the MCS information, and the CQI request included in anuplink grant at predetermined values, and notifying the mobile stationapparatus 3 of them. The mobile station apparatus 3 notified of anindication of transmission of an A-SRS (for example, indicated by onebit) and predetermined information set at a predetermined code pointthat gives an indication of transmission of only a CQI from the basestation apparatus 1 assigns only a CQI in a PUSCH (assigns the CQIwithout UL-SCH data), and transmits the PUSCH together with an A-SRS tothe base station apparatus 1 in the same subframe.

FIG. 5(b) shows a case where the frequency hopping flag, and theresource block assignment and hopping resource allocation informationare set at predetermined code points, as an example. That is, FIG. 5(b)shows a case where the first control information (predeterminedinformation) is composed of a frequency hopping flag, and resource blockassignment and hopping resource allocation information. When the firstcontrol information is a predetermined code point, the mobile stationapparatus 3 transmits an A-SRS without a PUSCH to the base stationapparatus 1. That is, when the frequency hopping flag, and resourceblock assignment and hopping resource allocation information (the firstcontrol information) that are predefined as predetermined informationare set at predetermined values, the mobile station apparatus 3transmits only an A-SRS without a PUSCH to the base station apparatus 1in a certain subframe.

In FIGS. 5(a) and 5(b), A-SRS transmission indication information ispredefined as control information included in the DCI format (uplinkgrant). Furthermore, an indication of transmission of an A-SRS can beperformed by using control information other than the A-SRS transmissionindication information. As the method, when the first controlinformation is a predetermined code point (predetermined value), themobile station apparatus 3 recognizes that an indication of transmissionof the second A-SRS is performed. Furthermore, at this time, the basestation apparatus 1 can also reuse the A-SRS transmission indicationinformation as a field for indicating other control information. Themobile station apparatus 3 can read control information that is not usedin the first control information as other control information (forexample, A-SRS configuration information).

Here, that the base station apparatus 1 instructs the transmission of anA-SRS by the transmission indication information of one bit indicatesthat the base station apparatus 1 notifies the mobile station apparatus3 of information that is included in an uplink grant and gives anindication of transmission of an A-SRS (A-SRS transmission indicationinformation), and thus, instructs the mobile station apparatus 3 toperform the transmission of an A-SRS. For example, the base stationapparatus 1 can indicate the mobile station apparatus 3 to performtransmission of an A-SRS by setting, at “1”, information that isincluded in an uplink grant and gives an indication of transmission ofan A-SRS, and notifying the mobile station apparatus 3 of it. That is,the base station apparatus 1 can indicate the mobile station apparatus 3to perform transmission of an A-SRS by setting control informationdefined for an indication of transmission of an A-SRS at a predeterminedvalue (for example, “1”), and notifying the mobile station apparatus 3of it. Here, when the base station apparatus 1 does not performtransmission of an A-SRS to the mobile station apparatus 3, the basestation apparatus 1 sets, at, for example, “0”, information that isincluded in an uplink grant and gives an indication of transmission ofan A-SRS, and notifying the mobile station apparatus 3 of it.

Furthermore, that the base station apparatus 1 gives an indication oftransmission of an A-SRS by control information (the first controlinformation) that is a predetermined code point (predetermined value)indicates that the base station apparatus 1 indicates the mobile stationapparatus 3 to perform the transmission of an A-SRS by setting, at apredetermined value, predetermined information of control information(any of the above-described control information) included in an uplinkgrant. For example, the base station apparatus 1 can indicate the mobilestation apparatus 3 to perform transmission of an A-SRS by: setting, atpredetermined values (for example, by setting all fields at “1”), thefrequency hopping flag, and resource block assignment and hoppingresource allocation information included in an uplink grant; andnotifying the mobile station apparatus 3 of them. Here, it is predefinedby specifications and the like, and is known between the base stationapparatus 1 and the mobile station apparatus 3 that the base stationapparatus 1 indicates the mobile station apparatus 3 to performtransmission of an A-SRS in accordance with what control information inan uplink grant is set and at what value the control information is set.That is, for example, the base station apparatus 1 can indicate themobile station apparatus 3 to perform transmission of an A-SRS by:setting, at predetermined values (for example, by setting all fields at“1”), control information defined for applications (for example, afrequency hopping flag, resource block assignment, and hopping resourceallocation) other than the indication of transmission of an A-SRS; andnotifying the mobile station apparatus 3 of them. Here, theabove-described control information (for example, indicated by one bit)defined for an indication of transmission of an A-SRS may be included inpredetermined information set at a predetermined value for the basestation apparatus 1 to indicate the mobile station apparatus 3 toperform transmission of an A-SRS.

By giving an indication of transmission of an A-SRS by controlinformation that is a predetermined code point, the base stationapparatus 1 can indicate the mobile station apparatus 3 to transmit onlyan A-SRS, irrespective of the value set in A-SRS transmission indicationinformation included in an uplink grant.

In the third embodiment, when an A-SRS transmission indication isindicated by transmission indication information of one bit in an uplinkgrant, the mobile station apparatus 3 transmits, to the base stationapparatus 1, a PUSCH and the first A-SRS in the same subframe.Furthermore, when the first control information is a predetermined codepoint, when indications of transmission of a PUSCH are received bydifferent uplink grants at the same timing, the mobile station apparatus3 may transmit a PUSCH to the base station apparatus 1 in a fourthsubframe from a subframe in which the uplink grants are received, andthe mobile station apparatus 3 may transmit the second A-SRS in theinitial cell-specific SRS subframe or mobile station apparatus-specificSRS subframe in the fourth and subsequent subframes from a subframewhere SRS indication information is detected in the uplink grant.Furthermore, a subframe transmitting the second A-SRS may be uniquelypredetermined in the system, may be notified from the base stationapparatus 1 to the mobile station apparatuses 3 as broadcast informationat a time, or may be notified from the base station apparatus 1 toindividual mobile station apparatuses 3.

Furthermore, in the third embodiment, when a DCI format including anindication of transmission of an A-SRS indicated by a predetermined codepoint is assigned in a CSS, another control information field that isnot used in the indication of transmission of an A-SRS may be used forthe group scheduling of transmission of an A-SRS.

In the third embodiment, the mobile station apparatus 3 can dynamicallyswitch the first A-SRS and the second A-SRS, can transmit it to the basestation apparatus 1, and can perform channel estimation tailored forcommunication environment, regardless of the presence or absence ofPUSCH transmission by indicating A-SRS transmission indication includedin an uplink grant by transmission indication information of one bit, orthe first control information that is a predetermined code point.

Furthermore, in the third embodiment, when PUSCH transmission is notnecessary, the transmission of an A-SRS can be performed without aPUSCH, and thus, the effect of interference in the other mobile stationapparatuses 3 can be reduced.

Furthermore, in the first to third embodiments, when an indication oftransmission of an A-SRS is included in a DCI format including anindication of transmission of a CQI, the mobile station apparatus 3 maytransmit, to the base station apparatus 1, a CQI and an A-SRS in thesame subframe, and may transmit them in different subframes.

Furthermore, in the first to third embodiments, when communication isperformed by using a plurality of unlink component carriers, thecorresponding parameter of the second A-SRS may be set for each unlinkcomponent carrier, or may be set for each the mobile station apparatus3.

According to the present invention, the base station apparatus 1 canindicate the mobile station apparatus 3 to switch the first A-SRS andthe second A-SRS and transmit it, in accordance with a communicationenvironment (including communication quality, channel quality, acommunication state, a channel state, and a radio channel state), theposition of the mobile station apparatus 3 (for example, a cell centerand a cell edge), and the number of the mobile station apparatuses in acell. For example, if the first A-SRS (inband A-SRS) assigned in a PUSCHresource is transmitted in an environment of poor communication qualityas in a cell edge, channel estimation accuracy is improved. Furthermore,if the second A-SRS (outband A-SRS) having a wider transmissionbandwidth that is assigned in a resource different from the PUSCH istransmitted in an environment of good communication quality as in a cellcenter, the improvement of communication quality due to frequencyselection scheduling can be provided. That is, it is possible to realizeeffective communication between the base station apparatus 1 and themobile station apparatus 3 by dynamically switching the first A-SRS andthe second A-SRS in accordance with a communication environment, or thelike.

Apart of functions of the base station apparatus 1 and the mobilestation apparatus 3 in the above-described embodiments may be realizedby a computer. In that case, a program for realizing these controlfunctions may be recorded on a computer readable recording medium, andthe program recorded on this recording medium may be read and executedby a computer system, thereby realizing the functions. The “computersystem” as used herein includes also OS and hardware such as aperipheral device. Furthermore, the “computer readable recording medium”refers to portable mediums such as a flexible disk, a magnetic opticaldisk, a ROM, and a CD-ROM, and a storage device such as a hard diskbuilt in a computer system. Furthermore, the “computer readablerecording medium” may include a medium dynamically holding a program fora short time, such as a communication line in a case where a program istransmitted through a network such as the Internet or the communicationline such as a telephone line, and a medium holding a program for agiven time, such as a volatile memory in a computer system serving as aserver or a client in the above-described case. Furthermore, theabove-described program may be one for realizing a part of theaforementioned functions, and further may be one for realizing theaforementioned functions by being combined with a program alreadyrecorded in a computer system.

Furthermore, a part or all of the mobile station apparatuses 3 and thebase station apparatuses 1 in the above-described embodiments may betypically realized as an LSI (Large Scale Integration) that is anintegrated circuit. Each functional block of the mobile stationapparatuses 3 and the base station apparatuses 1 may be individuallymade into chips, or may be made into chips by integrating a part or allof them. Furthermore, circuit integration techniques are not limited toLSIs, and may be realized by dedicated circuits, or general purposeprocessors. Furthermore, with the advent of circuit integrationtechnologies substituted for LSIs due to advances in semiconductortechnologies, it is also possible to use an integrated circuit using thetechnologies.

Hereinabove, although embodiments of the present invention has beendescribed in detail with reference to the drawings, specificconfigurations are not limited to these embodiments, and design and thelike without departing from the scope of the present invention are alsoincluded in the claims.

DESCRIPTION OF THE REFERENCE NUMERALS

-   1 base station apparatus-   3 mobile station apparatus-   101 transmission unit (base station side transmission unit)-   103 reception unit (base station side reception unit)-   105 scheduling unit (base station side scheduling unit)-   107, 207 higher layers-   108, 208 channel estimation unit-   109, 209 antenna-   201 transmission unit (mobile station side transmission unit)-   203 reception unit (mobile station side reception unit)-   205 scheduling unit-   206 reference signal generation unit-   1011, 2011 data control unit-   1013, 2013 modulation unit-   1015, 2015 radio transmission unit-   1031, 2031 radio reception unit-   1033, 2033 demodulation unit-   1035, 2035 data extraction unit-   1071, 2071 radio resource control unit-   2051 reference signal control unit

1. A mobile station apparatus comprising: transmission circuitryconfigured to transmit a sounding reference signal (SRS) in a singlecarrier-Frequency Division Multiple Access (SC-FDMA) symbolcorresponding to an SRS symbol, wherein the transmission circuitry isconfigured to, in a case that a region for SRS transmission on a givencomponent carrier is extended based on a higher layer signal, transmit afirst SRS in the SC-FDMA symbol, and transmit a second SRS in theextended region, the first SRS is an SRS transmitted based on a firsthigher layer signal, and the second SRS is an SRS transmitted based on asecond higher layer signal and an SRS request in a physical downlinkcontrol channel (PDCCH).
 2. A wireless communication method for a mobilestation apparatus, the wireless communication method comprising:transmitting a sounding reference signal (SRS) in a singlecarrier-Frequency Division Multiple Access (SC-FDMA) symbolcorresponding to an SRS symbol; and in a case that a region for SRStransmission on a given component carrier is extended based on a higherlayer signal, transmitting a first SRS in the SC-FDMA symbol andtransmitting a second SRS in the extended region, wherein the first SRSis an SRS transmitted based on a first higher layer signal, and thesecond SRS is an SRS transmitted based on a second higher layer signaland an SRS request in a physical downlink control channel (PDCCH).
 3. Abase station apparatus comprising: reception circuitry configured toreceive a sounding reference signal (SRS) in a single carrier-FrequencyDivision Multiple Access (SC-FDMA) symbol corresponding to an SRSsymbol, transmission circuitry configured to transmit informationrelated to a configuration of the SRS using a higher layer signal,wherein the reception circuitry is configured to, in a case that regionfor SRS transmission on a given component carrier is extended based on ahigher layer signal, receive a first SRS in the SC-FDMA symbol, andreceive a second SRS in the extended region, the first SRS is an SRSreceived based on a first higher layer signal, and the second SRS is anSRS received based on a second higher layer signal and an SRS request ina physical downlink control channel (PDCCH).
 4. A wireless communicationmethod for a base station apparatus, the wireless communication methodcomprising: receiving a sounding reference signal (SRS) in a singlecarrier-Frequency Division Multiple Access (SC-FDMA) symbolcorresponding to SRS symbol; transmitting information related to aconfiguration of the SRS using a higher layer signal; and in a case thatregion for SRS transmission on a given component carrier is extendedbased on a higher layer signal, receiving a first SRS in the SC-FDMAsymbol, and receiving a second SRS in the extended region, wherein thefirst SRS is an SRS received based on a first higher layer signal, andthe second SRS is an SRS received based on a second higher layer signaland SRS request in a physical downlink control channel (PDCCH).